Approval and Promulgation of Implementation Plans; State of New Mexico ; Grant County Sulfur Dioxide Limited Maintenance Plan

Technical Support Document

June 2014

OVERVIEW

T he EPA designated a portion of Grant County, New Mexico as a nonattai nment area for the 1971 sulfur dioxide ( SO2 ) national ambient air quality standard ( NAAQS ) o n S eptember 11, 1978 (43 FR 40412) . The area that was designated nonattainment is located within the Air Quality Control Region (AQCR) No. 012, and consists of a 3. 5 mile radius surrounding the former K ennecott Copper Corporation (now called the Chino Mines

- Hurley Facility ) and land above 6470 feet Mean Sea Level within an 8 mile radius of t he of the Hurley Smelter, which is part of the Chino Mines

- Hurley Facility in Hurley, New Mexico. New Mexico determined that

e missions from the Hurley S melter were the only known source of SO2 in the county and had caused the violations of the SO2 NAAQS that result ed in the area being designated nonattainment.

New Mexico’s reque st for redesignation of the Grant County nonattainment area to attainment and the first 10

- year maintenance State Implementation Plan (SIP) were approved by EPA on September 18, 2003 (68 FR 54672)

. The maintenance plan demonstrated that the area was expect ed to stay in attainment of the 1971 SO2 NAAQS for the initial maintenance period through 2015. The Clean Air Act, Section 175A requires that eight years after redesignation, the State must submit an additional revision of the SIP for maintaining the 1971 SO2 NAAQS for the second 10

- year period. On November 1, 2013, New Mexico submitted a Limited Maintenance P lan for the Grant County SO2 maintenance area to fulfill the Act’s requirement to submit a revision to the SIP for maintaining the standard for the second 10

- year period. The Limited Maintenance P lan SIP revision demonstrates that the area is expected to stay in attainment of the 1971 SO2 NAAQS through 2025. The revision also requests to disco ntinue the only SO2 monitor in the Grant Country maintenance area (the Hurley monitor, AQS ID 35

- 017

- 0003

- 42401

- 1) in light of the negligible SO2 concentrations measured at the monitor, and to implement an alternative SO2 monitoring methodology in its plac e.

The notice of public comment period and public hearing was published in the Silver City Daily Press and Independent on July 31, 2013. The public was also notified by posting the announcement in the New Mexico Register on July 31, 2013. NMED hosted an informational open house on the proposed SIP revision on September 4, 2013. A public hearing was held on October 8, 2013. The only written comments received by NMED during the public comment period were those from EPA Region 6.

CRITERIA FOR LIMITED MA INTENANCE PLAN OPTION

Since there are few specific content requirements defined in section 175A of the Act for maintenance plans, EPA has exercised its discretion in determining the required content. EPAalso has a Limited Maintenance Plan policy in effe ct for areas that can demonstrate consistent air

quality at or below 85% of the NAAQS for certain criteria pollutants , and our past precedent with respect other criteria pollutants is useful in assessing whether such an option is justifiable and appropriat e in the case for the SO2 NAAQS

. More specifically, EPA has developed guidance memoranda on a Limited Maintenance Plan approach specific to the ozone, particulate matter with an aerodynamic diameter less than 10 microns (PM10), and carbon monoxide NAAQS 1 :

 “Limited Maintenance Plan Option for Nonclassifiable Ozone Nonattainment Areas” from Sally L. Shaver, Office of Air Quality Planning and Standards, dated November 16, 1994

.

 “Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas” from Joseph Paisie, Office of Air Quality Planning and Standards, dated October 6, 1995

.

 “Limited Maintenance Plan Option for Moderate PM10 Nonattainment Areas” from Lydia Wegman, Office of Air Quality Planning and Standards, dated August 9, 2001

.

EPA has n ot issued guidance specific to the SO2 NAAQS, but we nevertheless have the authority to exercise our reasonable discretion and conclude that a limited maintenance plan option would be justifiable and appropriate in this case for the SO2 NAAQS. New Mexico has opted to develop a Limited Maintenance Plan for the Grant County SO2 maintenance area to fulfill the second 10

- year maintenance plan required by the Act. Taking the approach presented in past guidance memoranda, a limited maintenance plan i s available as an option to States who have demonstrated that the design values for SO2 in the maintenance area are at, or below, 85 percent of the NAAQS. As considered here, we believe it is sensible to use an 85 percent benchmark for the 24

- hour SO2 NAA QS, which corresponds to 0.119 parts per million (ppm). . There is currently only one monitor located in the Grant County maintenance area, the Hurley, New Mexico monitor (AQS ID 35

- 017

- 0003

- 42401

- 1). This monitor has been operating since 1997 and EPA dete rmined in a letter to NMED dated August 26, 2002, that the Hurley monitor was placed where modeling indicated the highest SO2 concentration was likely to occur. For this submission, the state provided data showing that the SO2 design value for the 24

- hour SO2 NAAQS (0.14 part per million (ppm)) has been 0.0 ppm for each of the five most recent years (2007

- 2011) for which certified ambient air quality data is available for the Hurley monitor. This data is presented in Table 1. The design values are significa ntly below the 85% threshold, making the Grant County maintenance area suitable for a Limited Maintenance Plan option. The area’s design value is significantly below the NAAQS, and it is reasonable to expect that there will not be NAAQS violations when ta king account of all anticipated emissions.

1 Copies of these guidance memoranda can be found in the docket for this proposed rulemaking.Table 1. SO2 M onitoring Data for Hurley Monitor 35

- 017

- 0003

- 42401

- 1

YEAR 24

- hour SO2 NAAQS

DESIGN VALUE (ppm)

2007 0.00

2008 0.00

2009 0.00

2010 0.00

2011 0.00

MAINTENANCE PLAN EL E MENTS

1. Attainment Emissions Inventory

The State’s submittal include s an emissions inventory to identify the level of emissions in the maintenance area that is sufficient to attain the NAAQS. The inventory should represent emissions during the same five

- year per iod associated with air quality data used to determine whether the area meets the applicability requirements of the limited maintenance plan option.

New Mexico’s Grant County Limited Maintenance Plan submittal includes an SO2 emissions inventory for Gr ant County Title V sources and Mi nor Point sources for the years 2007

- 2011 (see Table 2) . These base years represent the most recent emissions inventory data available and are consistent with the data used to determine applicability of the limited maintena nce plan option (i.e., design values at, or below, 85 percent of the 24

- hour SO2 NAAQS).

Table 2 . SO2 Emission Inventory for Grant County Title V Sources

YEAR ACTUAL EMISSIONS (SO2 tpy)

2007 4.14

2008 0.82

2009 4.66

2010 5.70

2011 6.57

The former Hurley Smelter, which is the source that caused the violations of the SO2 NAAQS that resulted in the area being designated nonattainment, was dismantled and its stacks removed in July 2006

. The Hurley Smelter was a copper ore smelter that was part of the ChinoMine

- Hurley Facility located in Hurley, New Mexico

. 2 The former Hurley Smelter was the only

major source of SO2 located within the maintenance area boundary. There are c urrently no major sources of SO2 located in the Grant County maintenance a rea. There are currently two Title V sources in Grant County (both located outside of the Grant County maintenance area): the Chino Mine and the Tyrone Mine. As shown in Table 2, t he combined actual SO2 emissions for the two sources has been no more than 6 .57 tons per year (tpy) for each of the years 2007

- 2011. The primary sources of SO2 emissions for both facilities are blasting fugitives and diesel generator engines. There are currently four minor point source s located within the Grant County maintenance area with combined annual allowable SO2 emissions of 316 tpy for each of the years 2007

- 2011. However, the actual SO2 emissions generated by these sources are minimal. This data supports New Mexico’s conclusion that the control measures contained in the original attainment plan will continue to protect and maintain the 1971 SO2 NAAQS in the Grant County maintenance area

. The New Mexico submittal supports a finding that t he requirement for an attainm ent emissions inventory is satisfied.

Table 3 . SO2 Emis sion s Inventory for Grant County Minor Point Sources

YEAR A NNUAL ALLOWABLE EMISSIONS (SO2 tpy)

2007 316.30

2008 316.30

2009 316.34

2010 316.34

2011 316.34

2 . Demonstration of Continued Attainment

To adequately ensure maintenance over the maintenance period, EPA has supported demonstrations with monitoring data that can show the area is significantly below a given NAAQS. In this case, the plan demonstrates the area meets air quality criteria conven tionally applied for limited maintenance areas (i.e., design value at or below 85% of the 24

- hour SO2 NAAQS , or 0.119 parts ppm ). There is no requirement to project emissions over the maintenance period. Instead, EPA has stated that if an area is at or bel ow 85 percent of exceedance levels, the air quality along with the continued applicability of PSD requirements, any control measures already in the SIP, and Federal measures, should provide adequate assurance of maintenance over the remainder of the 10

- yea r maintenance period. When EPA approves a limited maintenance plan, EPA is concluding that an emissions budget may be treated as essentially not constraining for the length of the maintenance period because it is unreasonable to expect that such an area wi ll experience so much growth in that period that a violation of the SO2 NAAQS would result.

2 The Chino Mine

- Hurley Facility modified its Title V and New Source Review (NSR) permi ts to remove all equipment and stacks associated with the former Hurley Smelter. A copy of the revised permit issued on May 23, 2007, is found in Appendix B of the State’s submittal.As discussed above, the state provided data showing that the SO2 design value for the 24

-

hour SO2 NAAQS (0.14 part per million (ppm)) has been 0.0 ppm for each of the five most recent years (2007

- 2011) for which certified ambient air quality data is available for the Hurley monitor. These values are below the 85% threshold demonstrating that a Limited Maintenance Plan option was a suitable decision for planning purposes

. The New Mexico submittal supports a finding that t he requirement for demonstrating continued attainment is satisfied.

3. Air Quality Monitoring

Over the course of the last 30 years, New Mexico has operat ed four SO2 monitors in the Grant County maintenance area. There have been no monitored exceedances of the 1971 SO2 NAAQS in the Grant County maintenance area since 1979. The only SO2 monitor currently located in the Grant County maintenance area is the Hu rley monitor (AIRS Monitor ID 35

- 017

- 0003

- 42401

- 1), which has been in operation since 1997. As discussed above, EPA determined in a letter to NMED dated August 26, 2002, that the Hurley monitor was placed where modeling indicated the highest SO2 concentrat ion was likely to occur. F ollowing the July 2006 dismantling of the Hurley Smelter, which is the source that was determined to be responsible for the violations of the SO2 NAAQS that resulted in the area being designated nonattainment

, m onitored SO2 concen trations have been negligible for the most recent five years for which certified ambient air quality data is available,. The state provided data from the Hurley monitor showing that the SO2 design value for the 24

- hour SO2 NAAQS (0.14 part per million (ppm )) has been 0.0 ppm for each of the five most recent years (2007

- 2011) for which certified ambient air quality data was available (see Table 1).

A. New Mexico’s Request to Modify the SO2 Monitoring Network :

Given the limited number of SO2 emission sources, the limited amount of SO2 emissions, and the negligible monitored SO2 concentrations in the Grant County maintenance area, New Mexico is requesting to discontinue SO2 air monitoring within the maintenance area

a nd to implement in its place an alternative SO2 monitoring methodology that does not utilize a gaseous analyzer for determining compliance with the SO2 NAAQS. The alternative SO2 monitoring method will consist of using PSD and Title V modeling and any requ ired post

construction monitoring for new and modified air quality permits and an annual emission review of all major SO2 sources located in the Grant County maintenance area. In the event that PSD or Title V modeling, PSD or Title V post

- construction moni toring, or the annual emissions review of major sources within the maintenance area indicate there is a significant increase in SO2 emissions that may cause a potential SO2 NAAQS violation, New Mexico will reinstitute a gaseous SO2 monitor at the Hurley, N M monitoring location (AIRS ID 35

- 017

- 0003

- 42401

- 1) or at a site expected to read greater SO2 levels than this site. If the monitored SO2 values after one year are at or below 50 percent of the 24

- hour or annual SO2 NAAQS, or both, the monitor would again be removed and the alternative SO2 monitoring methodology reinstated. The process would be repeated each time PSD or Title V monitoring, PSD or Title V post

construction monitoring, or the annual emission review of major SO2 sources within the maintenance area indicate a potential SO2 NAAQS violation.B. Does Modification of the SO2 Monitoring Network Meet the Monitoring Network

Modification Requirements under 40 CFR section 58.14(c)?

To verify the attainment status of the area over the maintenance period, the maintenance plan should contain provisions for continued operation of an appropriate, EPA

- approved air quality monitoring network, in accordance with 40 CFR part 58. Over the course of the last 30 years, New Mexico has operated four SO 2 monitors in the Grant County maintenance area. There have been no monitored exceedances of the 1971 SO 2 NAAQS in the Grant County maintenance area since 1979. The Hurley monitor (AIRS Monitor ID 35

- 017

- 0003

- 42401

- 1), which has been in operation since 1997 , is the only SO 2 monitor currently operating in the Grant County maintenance area. EPA determined in a letter to NMED dated August 26, 2002, that the Hurley monitor was placed where modeling indicated the highest SO 2 concentration was likely to occur. Mon itored SO 2 concentrations have been negligible for the most recent five years for which certified ambient air quality data is available, following the July 2006 dismantling of the Hurley Smelter, which was the source originally responsible for the violatio ns of the SO 2 NAAQS that resulted in the area being designated nonattainment. The state provided data from the Hurley monitor showing that the SO 2 design value for the 24

- hour SO 2 NAAQS (0.14 part per million (ppm)) has been 0.0 ppm for each of the five mo st recent years (2007

- 2011) for which certified ambient air quality data was available. In light of the limited number of SO 2 emission sources, the limited amount of SO 2 emissions, and the negligible monitored SO 2 concentrations in the Grant County maint enance area, New Mexico is requesting to discontinue SO 2 air monitoring within the maintenance area, as currently required by its maintenance plan, and to instead implement an alternative SO 2 monitoring methodology that does not utilize a gaseous analyzer for determining compliance with the SO 2 NAAQS. The alternative SO 2 monitoring method will consist of using PSD and Title V modeling and any required post

- construction monitoring for new and modified air quality permits and an annual emission review of all major SO 2 sources located in the Grant County maintenance area. In the event that PSD or Title V modeling, PSD or Title V post

- construction monitoring, or the annual emissions review of major sources within the maintenance area indicate there is a signific ant increase in SO 2 emissions that may cause a potential SO 2 NAAQS violation, New Mexico will reinstitute a gaseous SO 2 monitor at the Hurley, NM monitoring location (AIRS ID 35

- 017

- 0003

- 42401

- 1) or at a site expected to read greater SO 2 levels than this s ite. If the monitored SO 2 values after one year are at or below 50 percent of the 24

- hour or annual SO 2 NAAQS, or both, the monitor would again be removed and the alternative SO 2 monitoring methodology reinstated. The process would be repeated each time PS D or Title V monitoring, PSD or Title V post

- construction monitoring, or the annual emission review of major SO 2 sources within the maintenance area indicate a potential SO 2 NAAQS violation. We accordingly find that with the alternative SO 2 monitoring me thodology in place, the Hurley monitor is no longer required as part of the 24

- hour SO 2 maintenance plan. By our approval, the maintenance plan will not contain any contingency measures to be triggered by a monitored air quality concentration. NMED may sub mit a separate request for a system modification (including a request for discontinuation of a State or local air monitoring station) for EPA’s review and approval under the bases provided in 40 CFR § 58.14. We find that the State has satisfied the monitor ing network and verification of continued attainment requirements for the limited maintenance plan.4

. Contingency Measures

Section 175A(d) of the CAA requires that a maintenance plan include contingency provisions, as necessary, to promptly correct an y violation of the NAAQS that occurs after the area is redesignated to attainment. Under section 175A(d), contingency measures do not have to be fully adopted at the time of redesignation. However, the contingency plan is considered to be an enforceable pa rt of the SIP and should ensure that the contingency measures are adopted expeditiously once they are triggered by a specified event. The general approach for contingency measures discussed in the limited maintenance plan guidance memoranda provide that th e contingency provisions should identify the measures to be adopted, a schedule and procedure for adoption and implementation, and a specific time limit for action by the State. However, the General Preamble for the Implementation of Title I of the Act Ame ndments of 1990 (57 FR 13498) states that SO2 provisions require special considerations. A primary reason is that SO2 control methods are well established and understood. Therefore, contingency measures for SO2 need only consist of a comprehensive program to identify sources of violations of the SO2 NAAQS and to undertake an aggressive follow

- up for compliance and enforcement.

There are currently no major SO2 sources within the Grant County maintenance area. In the event that an SO2 source(s) moves into or within close proximity to the Grant County SO2 maintenance area, New Mexico will ensure that such source(s) will comply with all applicable state and federal SO2 regulations and requirements. New Mexico is also committing to maintain a comprehensive com

pliance and enforcement program to identify sources of violation of the SO2 NAAQS within the maintenance area and to undertake aggressive follow up measures to ensure compliance with the SO2 NAAQS. In conformance with CAA section 175A(d), New Mexico will a lso implement all measures with respect to the control of air pollutants concerned which were contained in the SIP for the area before redesignation of the area as an attainment area, to the extent such measures are applicable to any sources which may exis t at the time of any NAAQS exceedance. We believe that New Mexico’s contingency plan is adequate for identifying which SO2 sources are responsible for violations of the 1971 SO2 NAAQS and undertaking aggressive measures to ensure compliance of the SO2 NAAQ S to the submittal supports a finding that New Mexico’s contingency measures plan is approvable.

CONCLUSION

New Mexico followed all applicable administrative procedures and provided the technical jus tification to demonstrate that t h e second 10

- year plan for maintenance of the SO2 NAAQS is adequate to protect human health and the environment in the Grant County maintenance area. New Mexico has also provided information to demonstrate that discontinuance of the Hurley monitor is in acco rdance with the monitoring network regulations for system modifications under 40 CFR section 58.14

. We recommend approval of the second 10

- year plan for maintenance of the SO2 NAAQS in the Grant County maintenance area. We also recommend approval of New Me xico’s request to discontinue operation of the Hurley monitor in the Grant County maintenance area.